The present invention relates to a surveying instrument for performing light wave distance measurement by projecting a laser beam to an object to be measured. In particular, the present invention relates to a surveying instrument, which comprises a zooming function to continuously magnify an angle of view of a collimated image.
First, description will be given on a conventional type surveying instrument referring to FIG. 7.
FIG. 7 represents a surveying instrument main unit 1. The surveying instrument main unit 1 is installed on a tripod (not shown).
The surveying instrument main unit 1 primarily comprises a leveling unit 2 mounted on a tripod, a base unit 3 mounted on the leveling unit 2, a frame unit 4 mounted on the base unit 3 so that the frame unit 4 can be rotated horizontally around a vertical axis, and a telescope unit 5 mounted so that the telescope unit 5 can be rotated around a horizontal axis on the frame unit 4 in a top-to-bottom direction.
The frame unit 4 comprises a display unit 6, an operation unit 7, and a control unit provided inside (not shown), etc. The telescope unit 5 comprises a first telescope 8 which is a simple collimating telescope and a second telescope 9 which has fixed high magnification, which collimate an object to be measured. Further, the first telescope 8 and the second telescope 9 have optical axes running in parallel to each other. The second telescope 9 has high magnification. For example, magnification of the second telescope 9 is 30 times (30×).
On the telescope unit 5, there are provided a collimating optical system including the first telescope 8 and the second telescope 9 and a distance measuring optical system. After a collimating position (a measuring point) has been determined by the first telescope 8 and the second telescope 9, light wave distance measurement is performed via the distance measuring optical system.
In case the collimating position is to be determined, because the second telescope 9 has high magnification and has narrower visual field, a collimating direction is roughly determined by the first telescope 8, which has wider visual field. Further, the collimating position is determined by the second telescope 9.
In the conventional type surveying instrument, collimation is performed by the first telescope 8 which is a simple collimating telescope and the second telescope 9 which has fixed high magnification. When the collimating direction is determined or the object to be measured is collimated by the first telescope 8 and the collimating position is to be determined by the second telescope 9, magnification is very much different between the two telescopes. As a result, the collimating position or the object to be measured may be out of the visual field of the second telescope 9. In this case, the collimating direction must be adjusted again by the first telescope 8.
Or, when the collimating position is determined by the second telescope 9, it may be wanted sometimes to observe more closely around the collimating position. Because the second telescope 9 has fixed magnification, it is not possible to observe more closely than the visual recognition by the second telescope 9.
A zoom lens is used in optical instruments such as a camera, and the magnification can be changed without changing the collimating direction. However, when magnification is changed by the use of the zoom lens, the collimating position is moved within the visual field. In this respect, this is not adopted for a surveying instrument, which requires high accuracy.
A surveying instrument comprising the first telescope 8 and the second telescope 9 is disclosed in JP-A-2003-27935.